Non-flammable, thin, integrally illuminated control panel overlay

ABSTRACT

A non-flammable control panel overlay with legible indicia openings, integral illumination and integral supporting means comprises a metallic member with indicia openings on the front thereof backed by a non-flammable, transparent backing member mounted in a recessed area on the back of the member behind the indicia openings, an electroluminescent lamp mounted in a second recessed area behind the transparent backing member and ribs on the back side of the member comprising the unetched areas left when the various mounting recesses are formed. Such a metallic overlay is made by mechanically engraving the indicia, on the front of a metal blank and then chemically etching the rear of the blank, in a stepwise fashion to form the various recesses and remove unnecessary material, until breakthrough to the indicia occurs.

United States Patent Kldd, Jr. et a]. [451 July 18, 1972 [541NON-FLAMMABLE, THIN, 3,284,941 11/1966 Kaup .40/130 M INTEGRALLYILLUMINATED 2,707,346 5/1955 Fuller, Jr. ..40/l33 CONTROL PANEL OVERLAYPrimary ExammerRobert W. Michell [72] Inventors: Thomas L. Kidd, Jr.,Norristown; Albert Assistant Examiner-Richard Carter D. McClain, Jr.,Philadelphia, both of Pa. AttorneyPaul F. Prestia, Allen E. Amgott,Melvin M. Goldenberg, Henry W. Kaufmann, Frank L. Neuhauser and Oscar[73] Ass1gnee. General Electric Company B wadde" [22] Filed: July 27,1970 [21] Appl. No.: 64,879 [57] ABSTRACT A non-flammable control paneloverlay with legible indicia Related ApPucafinn openings, integralillumination and integral supporting means [62] Division of 706,044 61968 Patent comprises a metallic member with indicia openings on the 3,5 80 7 5 5 front thereof backed by a non-flammable, transparent backingmember mounted in a recessed area on the back of the 52 us. Cl 40/130M40/133 member behind the indicia elemduminescem [51] Int G09f 13/22 lampmounted in a second recessed area behind the trans- [58] Field of Search..4o/i'5dM"i'55"'i'33 A 133B backing member and ribs the back Sidemember comprising the unetched areas left when the various [56]References cued mounting recesses are formed. Such a metallic overlay ismade by mechanically engraving the indicia, on the front of a metalUNITED STATES PATENTS blank and then chemically etching the rear of theblank, in a 3 4 stepwise fashion to form the various recesses and removeuni'g 'ggg i a necessary material, until breakthrough to the indiciaoccurs.

u er 3,038,271 6/1962 Macl-lutchin et al ..40/130 M 2 Claims, 4 DrawingFigures NON-FLAMMABLE, THIN, INTEGRALLY ILLUMINATED CONTROL PANELOVERLAY This application is a division of our application Ser. No.706,044, filed Feb. 16, 1968, now US. Pat. No. 3,580,755.

INTRODUCTION The invention herein described was made in the course of orunder a contract with the Department of the Air Force.

This invention relates to a non-flammable control panel overlay suitablefor use in aircraft and spacecraft. More specifically it pertains tosuch overlays which are thin, selfsupporting and integrally illuminated.

BACKGROUND OF THE INVENTION In the interest of weight reduction andspace saving in and around the cockpit areas of aerospace vehicles,numerous efforts have been made to reduce the weight and volume ofcontrol panel display assemblies. Among the results of these efforts aredisplays which include a panel overlay comprised of transparent plasticmaterial with electroluminescent or small incandescent lamps embeddedtherein. Replacement of individual embedded lamps in these overlayswithout replacement of the whole overlay is difficult if not impossible.Further, because such plastic overlays have little inherent stiffness,they usually require a backing member for support. Undesirable extraweight results because of the use of such support.

The biggest disadvantage of these plastic overlays, however, is theirflammability. The organic matter contained in these overlays adds to thefire hazard present in any cockpit. Minimization of this hazard is oneof the objectives of the present invention.

While metallic control panel displays would avoid the flammabilityproblem of plastic overlays, no practical means for providing integrallyilluminated indicia therein has been known. In addition to the bulk andweight of bulbs, sockets and mountings therefor, another factorinhibiting the use of metallic displays has been difficulty in producingclear lettered indicia openings in thin metallic face members. The

present invention is also directed to that problem.

A general object of the present invention is to provide a thin,non-flammable, integrally illuminated panel assembly.

Another object is to provide a non-flammable, lightweight, integrallyilluminated, self-supporting panel overlay.

A further object of this invention is to provide an inexpensive, easilymanufactured, integrally illuminated, non-flammable panel overlayincluding highly legible illuminated character openings therein.

It is also an object to provide improved methods for making metalliccontrol panel overlays with precisely formed character openings therein.

BRIEF DESCRIPTION OF THE INVENTION These and other objects are met, inaccordance with the present invention, by a metallic overlay withindicia openings therein, a non-flammable, flat, transparent backingmember mounted in a recessed area behind the indicia openings, and anelectroluminescent lamp mounted in a second recessed area behind thetransparent backing member. The overlay may also include integralsupporting ribs on the back side thereof.

The necessary character openings and recesses and integral reinforcementribs on the back side of the overlay are made preferably by mechanicallyengraving the front of the overlay in the shape of the characteropenings desired and applying a temporary support material, such as amaskant, to the whole overlay including the first engraved areas.Recesses are then chemically etched, in stages, on the back of theoverlay, exposing from the reverse side the previously engravedcharacters and providing mounting seats for a permanent transparentsupport member behind the etched character openings and for anelectroluminescent lamp behind the transparent support member. Unetchedareas on the back of the overlay provide integral supporting ribstherefor.

DETAILED DESCRIPTION OF THE INVENTION While the specification concludeswith claims particularly pointing out and distinctly claiming thesubject matter of the present invention, this invention may be betterunderstood from the following description, taken in conjunction with thefollowing drawings, in which:

FIG. 1 is a front view of a control panel overlay comprising thepreferred embodiment-of the present invention;

FIG. 2 is a rear view of the overlay shown in FIG. 1;

FIG. 3 is a cross section of the overlay shown in FIGS. 1 and 2; and

FIG. 4 is a rear view of a metal blank engraved and etched in accordancewith the present invention to produce the overlay shown in FIGS. l-3.

Referring more specifically to FIG. 1 there is shown an anodizedaluminum overlay l with indicia openings 2 and a control switch 3.

In FIG. 2 the rear of overlay 1 is seen with switch 3 removed. Also seenin FIG. 2 are integrally formed supporting ribs 4 for the overlay 1 andelectroluminescent lamps 5 including necessary connectors and wiring.

A cross section of the same control panel overlay is shown in FIG. 3, inwhich is also shown, a flat transparent backing member 6, specifically apiece of zinc borosilicate glass, mounted behind indicia openings 2 in arecessed area 7. Mounted behind backing member 6 in a second recessedarea 8 is an electroluminescent lamp 5. The connectors and connectingwire for electroluminescent lamp'5 as well as control switch 3 isomitted from FIG. 3 for purposes of clarity.

Other materials may, of course, be substituted for those describedabove. However, the overlay 1 will generally be comprised of a metallicmaterial for purposes of non-flammability. Zinc borosilicate glass isselected in the preferred form of the present invention for thetransparent backing member because of its flexibility and hightemperature resistance relative to other glasses and for itsnon-flammability relative to plastics. Transparent backing member 6,bonded generally with a chemically adhesive such as an epoxy cement inrecessed area 7, supports the free centers of indicia openings 2.Backing member 6 may be tinted to control color or brightness in theilluminated indicia openings.

In use, the metallic overlay of the present invention is eitherassembled with a dust cover on the back thereof or mounted on some formof control panel backing member.

To produce the highly legible indicia openings in the overlays of thepresent invention, the indicia are first mechanically engraved on oneside of a metal blank to a uniform depth somewhat less than the blankthickness. The remaining unengraved thickness holds the free centers ofthe indicia characters and makes possible very precise characterformation. Support material is then applied to the engraved side of theblank and the reverse side is chemically etched. When this process iscomplete the thickness of the blank in the area surrounding the indiciais sufficiently reduced to expose the indicia on the reverse side of theblank. Openings in the shape of complex indicia characters are thusformed with good precision. In the process of chemical etching the backside of the indicia, mounting recesses for backing member 6 and lamps 5may also be formed and excess material around integral supporting ribsmay be removed.

For example, the metallic overlay shown in FIGS. l-3 was made from afive inch by seven inch blank of 0.091 inch thick 7075-T6 aluminum. (Inother examples, 606l-T6 aluminum has also been used with equal success.These materials are commercially recognized as structural grade aluminumalloy.)

A rear view of this metal blank following engraving and etching is seenin FIG. 4. The indicia were formed on one side of the blank, bymechanical engraving, to a flat depth of 0.01 inch, with a cutter havinga side taper on the order of 3. Generally the width of the indiciacharacter lines was about 0.026 inch and the ratio of line length toline width was about 6 to l.

To control glare from the front. of the panel and to improve itsappearance, the blank was anodized, by a conventional anodizationprocess, after it had been mechanically engraved.

A chemical etch maskant coating, specifically Organocerame, Inc. maskantno. 1-1010, was then flow coated on both sides of the blank. Afterallowing the maskant to dry it was cut and removed in the area definingbacking member recess 7. This exposed area was then etched to a depth of0.01 inch with a conventional sodium hydroxide etchant bath at l80200 F.Typically, this bath was made up of ounces of sodium hydroxide crystals,0.3-0.4 ounces of sodium gluconate and 0.2-1.0 ounces of sodium sulfideper gallon of water. (Other maskants, other sodium hydroxide baths, andother types of etchants, such as hydrochloric acid baths, have beenused.)

Maskant was then cut and removed from the area defining lamp mountingrecess 8 and the area 9 surrounding supporting ribs 4 which arealternatively describable as unrecessed areas. These areas were etchedwith the conventional sodium hydroxide etchant described above untilbreakthrough to the flat bottomed indicia engraving was achieved. Therecessed areas produced by the two step etching process just describedare seen most clearly in FIG. 4.

The complex indicia characters thus formed by the combined mechanicalengraving-chemical etch procedure of the present invention are muchsuperior in sharpness and legibility to any heretofore known to havebeen produced by either mechanical or chemical means alone.

In order to complete the metallic overlay produced as described above,it is necessary to provide a permanent supporting means for the areasurrounding, and the free centers of the indicia openings. It is alsonecessary to remove the remaining maskant from the overlay.

In the preferred form of the present invention a zinc borosilicatebacking member 6 is bonded with a conventional epoxy cement in recess 7.A problem arises however in that the epoxy cement makes it difficult toremove the maskant from the front of the overlay. Therefore it has beenfound best to apply a polyvinyl alcohol (PVA) parting layer and asilicone rubber overcoat to the back of the indicia after the chemicaletching process. The maskant is then easily removed from the front ofthe overlay and a PVA parting layer and silicon rubber overcoat isapplied to the front of the overlay. After removing the previouslyapplied PVA-silicone from the back thereof, the glass backing member maybe permanently bonded in place. The PVA-silicone on the front of themetallic panel overlay is then easily removed without damage to theindicia openings.

While the foregoing invention has been described with reference toparticular embodiments thereof for purposes of clarity and convenience,it should be understood that numerous modifications may be made by thoseskilled in the art without departing from the inventions true spirit andscope. Therefore the appended claims are intended to cover all suchequivalent variations as come within the true spirit and scope of thepresent invention.

What we claim as new and desire to secure by letters patent of theUnited States is: y

l. A control panel overlay comprising a thin, sheet-like metallic memberhaving a first recessed area on the back thereof, a second recessed areawithin and smaller than said first recessed area, indicia openingsthrough said overlay in said second recessed area, a flat, transparentbacking member for support of said indicia openings and the free centerssurrounded by said openings, said backing member conforming to the shapeof and seated in said second recessed area, and an electroluminescentlamp conforming to the shape of and seated in said first recessed area.

2. A control panel overlay, as recited in claim 1, further includingadditional recessed areas of predetermined shape and depth, theunrecessed areas surrounding all of said recessed areas being adapted toprovide integral structural support to the overlay. at

1. A control panel overlay comprising a thin, sheet-like metallic memberhaving a first recessed area on the back thereof, a second recessed areawithin and smaller than said first recessed area, indicia openingsthrough said overlay in said second recessed area, a flat, transparentbacking member for support of said indicia openings and the free centerssurrounded by said openings, said backing member conforming to the shapeof and seated in said second recessed area, and an electroluminescentlamp conforming to the shape of and seated in said first recessed area.2. A control panel overlay, as recited in claim 1, further includingadditional recessed areas of predetermined shape and depth, theunrecessed areas surrounding all of said recessed areas being adapted toprovide integral structural support to the overlay.